The present disclosure relates to toner compositions with toner particles having a core-shell type structure and purine derivative antiplasticizers in the core and/or shell. More particularly, embodiments herein relate to hybrid toner compositions. The toner compositions described in the present disclosure prevent toner blocking phenomenon by controlling (e.g., lowering) the circularity of the toner particles. The avoidance of toner blocking leads to improvement of transfer efficiency, developability, cleanability, and flowability, which ultimately provide better print quality. More specifically, “lowering” the circularity of the toner particles means designing toner particles with less-than-spherical shape which translates to a circularity measurement of less than 1.00, or more specifically, less than or equal to 0.980, or between 0.940 to 0.980.
When toner is prepared using a pulverization method, it is inevitable that wax becomes embedded in the surface of the toner and protrudes outwardly during the pulverization step. This causes what is referred to as a toner blocking phenomenon, resulting in low image quality and poor storage stability of the toner. Blocking is a phenomena where toner is subject to a high temperature softens on its surface and toner particles coagulate or stick together. Once blocking occurs, the flowability during storage or in the developing unit radically drops, which makes transporting toner to the developing roller difficult and can be detrimental to image quality.
Various attempts have been made in the field to prevent toner blocking phenomenon, but have been unsuccessful. For example, replacing a high percentage amount (e.g., 40% by weight) of the polyester with styrene/acrylate did not help in lowering the circularity of the toner. Likewise, altering the conditions of the toner making process, such as for example, lowering the coalescence temperature or increasing the coalescing pH only worsen the surface morphology of the toner to change from semi-smooth to very rough, and did not change the toner circularity.
Therefore, there exists a need to prevent toner blocking phenomenon in toner compositions, while maintaining the right molecular weight for their fusing properties.